Armored electric conductor.



P. SGHRODER.

ABMOBED BLECTRIG CONDUCTOR. .APPLICATION FILED JUNE 20, 1908.

956,1 86. Patented Apr. 26, 1910.

' PAUL SCHRDER, 0F STUTTGART, GERMANY.

ABIORED ELECTRIC CONDUCTOR.

Specification of Letters Patent.

Application led J'une 20, 1908: Serial No. 439,505.

ments in armored electric conductors of that.

class in which the wires are embedded in an insulating material and surrounded by a sheet-metal coverin or sheath. The sheetnietal coverings o these lconductors were heretofore closed by interlocking folds. The

. sheet-metal used for the coverings was either steel, brass, copper or other material. As it has to be capable of strong resistance, hard metal has to be employed for the covering or sheath. Such inclosed conductors, however, were vdifficult to bend as at the interlocking folds or seam four layers of hard metal are superposed. It is therefore impossible to lay these conductors at sharp curves and'hends, as there is a danger that the' hard but still brittle material may break in bending. There is, however, another ob- ]ection to the armored electric conductors heretofore in use. Itis well known that ythe exterior coverin or sheath is used as a conductor for the e ectric current; for instance, in the three-wire systems, as the intermediate' conductor. This intermediate conductor has to of such dimensions that its electrical resistance is in a certain proportion to the y electrical resistance of the interior wires. As

the coverings ofall inclosed conductors are usually ma e of the same sheet-metal so as to simplify the manufacture, the covering has, in ependently of the electrical resistance of thel interior conductors, for lthe saine diameter of the conductor throughoutthe same resistance. Y Y

The object of this invention is to obvia-te the objections referred to and to supply an' armored electric conductor in which they are completely and effectivelyobviated; and for this purpose the invention consists of an armored electric conductor in which the covermg or sheath is rovided atthe adjacent id d with (ntwb y-bent-folds and tightly e ion a. connectin stri having igfrdly-nt interloclng edgs, and 1n which the` material uid-the conductivity of the coveringis in certain proportion to the conductivity of Bie interior conductors.

'sheet-metal covering or In the accompanying drawings, Figures l and 2 are vertical transverse sections of my improved armored electric conductor, showing two different constructions of the same, Fig. 3 is a perspective view of the improved conductor, showing the arrangement of a branch-connection for the same and Fig. 4 is a vertical transverse section of the branchconnection.

Similar letters of reference indicate corresponding parts.

The interior conductors a and b are surrounded in the usual well-known manner by solid insulating'material c and are inclosed by a tubular coverin of-connecting the e ges of the covering or sheath d by a seam formed of bent and interlocking folds, the adjacent edges of the sheath are bent in outward or inward direction so as to abut at their bent portions, and connected by a sheet-metal strip e the edges of which are bent inwardly so as togengage with the outwardly or inwardly bent folds of the coveror sheath d, according as the clamping strip is located at the outside or at the inside of the covering, as shown respectively in Figs. 1 and 2. The connection of the covering orA sheath is therefore obtained by means of a clamp, means of an interlocking seam. It is true that the material of the covering or sheath atA the point of connection is likewise a fourfold one, but it is not absolutely necessary that the clamping stri should be of thesame material as the s eath. On the contrary, without impairing the durability of the armored conductor, it can be made of a softer or thinner sheet-metal that can be bent with great facility. The clamping strip, which serves as permits furthermore, in a similar manner as the conductors heretofore in use, to bring the electrical resistance .of the covering or sheath in certain ro ortionate relation with the resistance o t e interior conductors. The clamping strip can also be made from a metal by trical resistance of the covering or sheath is increased or diminished; or it can be made conductivity, that is to-say, the strip e can -be made of another material than the sheath itself. The ed? of the sheath can be bent outwardly, as own inVFig. 1, or inwardly, as shown in Fig. 2, the clamping strip being the .locking device,-

iatented Apr. 26, 1910.

or sheath d. In place and not, as before, by

. the conductors having interlocking folds or. seams. This advantage is found at the omts Where branch-connections are lmade.`

n the well-known armored electricconductors, the conductor had to be interrupted at the branch-connection and a special box had to be used. Such a branch-connection does not only take up considerable time in making it, but has the objection that-the electric connection is made by means of clamps or clamping screws, which, as Well known, 'form the' cause of loss of current, as in the course of time the spring-clamps lose their v'tightness or Ithe screws are loosened by unavoidable vibrations.

The improved conductor facilitates the arrangement ofa branch-connection, as shown in Fig. 3. All thatl is necessary, is to remove at the point Where the branch is to be made, a portion of .the covering or sheath, but Without removing the locking strip e, which connects the two ends of the covering or sheath, las before, across the point Where the branch-connection -is located. The insulating material is then removed irom the yWires a and b, which latter are stretched and slightly bent and then connected With the branch-conductors al, b1 inV the usual manner, soldered together, and

tem in which the insulatln finally covered .by any suitable insulating strip or band, placed around the Wires. `The oint of contact between the main and ranch conductors is then much better and more reliable than when made according to the old style. offers no greater diiicu ty than the o d sysmaterial has to be removed from the con u'ctors When the branch-connection is made, While it is much cheaper as the branch-box heretofore used is dispensed with.

Having thus described my invention, I claim as new and desire to secure by Letters Patent:

In an armored electric conductor, the combination of interior Wires surrounded by insulating material a portion of which has been removed whereby a portion of said Wires is bared, metal coverin sheaths inciosing said material on each side oi the space from The im roved arran ement which the insulating materiai is removed,

said covering having bent-over `side-edges, branch-conductors connected directly .with the baredA portion of the interior Wires, and a clamping strip` having bent-over edges interlocking with the bent-over edges of the covering sheaths, and extending across said bared portions and connecting said sheaths. ln testimony, that I claim the foregoing as my invention, l'. have signed my name in presence of two subscribing Witnesses.

PAUL SCHRDER. Witnesses:

. Amann Stirnn, v About GnnHAUsnn. 

